Our long term objective is to determine the role of DNA repair in the evolution of recombination. By studying the relationship of recombination to genetic repair, we hope to advance the understanding of what we think are two related problems. First, is the problem of how living systems have evolved in cope with agents with cause genetic damage and, hence, cancer. Second, is the problem of the evolutionary function of recombination. The proposed work will test in the eubacterium Bacillus subtilis the hypothesis that natural genetic transformation evolved because of its role in DNA repair. To test this hypothesis we propose (1) to continue our studies of the survivorship of transformed and untransformed cells, (2) to test whether chromosomal sites of recombination are random or coincident with respect to sites of DNA damage, (3) to determine the levels of the major B. subtilis recombination protein in competent and non-competent subpopulations following DNA damage to a competent cell culture, (4) experiments to isolate competent cells from noncompetent cells and to measure their relative frequencies and survivorship in the presence of varying amounts and kinds of damaging agents, (5) studying spontaneous transformation mediated between cells instead f between recipient cells and purified donor DNA, as a step towards determining the mechanisms of transformation under natural conditions, and (6) selection experiments to increase the rate of transformation by selecting survivors of treatment with DNA damaging agents.